This reminds me of the Parasite maps from Warcraft 3, put into a pixelated indie game, and with specialized characters. Not necessarily a bad thing; I was pretty good at those.
I'll have to check this out later tonight.
Yes. There was one, an Aliens mod. One player started as the queen, inside another player, after 30 seconds queen could pop out, transforming their host into a normal alien. (the Queen could wait up to an additional 90 seconds if she chose, she got identical Exp to her host and the timing/positioning of her emergence could change the game, even ensure an instant alien loss). There's hordes of NPC aliens, you level up by killing them. Alien players can transform between alien and human, they too leveled by killing NPC aliens as humans (as humans, the NPCs treated an alien player like a human - in alien form the NPC aliens ignored alien players). There were turrets that could and would shoot at any/all aliens they saw (an alien player in alien form was detected, but could force the turret to stop shooting by changing back to human form.... no AI in that targeting system!) and there was an oxygen plant to sabotage and a mechanical suit that Alien players -could not enter-, but any human inside could not be killed until that very strong suit was destroyed.
A human player killed by an NPC alien left the game, unless he'd been affected by a facehugger at the time. All human players killed by PC aliens became alien players. Alien players killed by anything left the game. Game went for a max of 15 minutes, alien players won by killing/transforming all human players before then, humans won by killing all alien players before then or by still being human at the 15 minute mark.
It was incredibly fun for me to play that game as either human or alien. It wasn't mafia-like though, typing took time out from killing NPC aliens (that EXP was priceless) and any time you spent with the chat window open (or reading what others wrote) was time you could not spend being ready to defend yourself (and an alien attacking a human could kill them in about 3 seconds from full health).
Man oh man I miss that game. Boo-hiss that there are so many bot-game hosts these days, so players can never find real games or each other anymore.